High-power RF devices and other high-frequency devices have achieved wide popularity in recent years, particularly in cellular base-station applications, where it is desirable to provide high instantaneous bandwidth at a fairly high power level. Due to the nature of RF power devices, however, it is often necessary to employ impedance transformation circuitry in conjunction with the amplifier output.
Prior art impedance transformation circuits typically include a shunt inductance element in series with a large capacitor configured to provide DC blocking. Such shunt capacitors may, for example, be on the order of 200 pF for a 50 W RF power device. The resonant frequency of DC blocking capacitors combined with the presence of an external bias (which has its own effective capacitance and inductance) greatly limit the low frequency instantaneous bandwidth of an amplifier. Thus, the use of traditional shunt output match circuits will become increasingly undesirable as the need for greater bandwidth increases. Furthermore, the use of large capacitors often results in output match losses (Q).
Accordingly, it is desirable to provide output match circuitry with an appropriate base-band (low-frequency) resonant frequency and greater instantaneous bandwidth. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.